Heat-resistant resins and laminates



. 2,936,260 HEAT-RESISTANT RESINS AND LAMINATES George Alexander,Pittsfield, Mass., assignor to General Electric Company, a corporationof New York No Drawing. Application July 2, 1956 Serial No. 595,081

9 Claims. (Cl. 154-128) This application is a continuation-in-part of mycopending and now abandoned application Serial No. 359,- 967, filed June5, 1953, and assigned to the same assignee as the present invention.

This invention relates to heat-resistant resins produced from specificphenol-aldehyde condensates and unsaturated ethers of polymethylolphenol and which are eminently suited for the manufacture oflaminatedproducts. The invention includes both thermosetting compositions andlaminates made therefrom.

The novel compositions of the present invention comprise (1) athermosetting, partially reacted, aqueous phenolic resin prepared byreacting a phenol with an excess of an aldehyde in the presence of acatalyst selected from the group consisting of calcium hydroxide andbarium hydroxide, neutralizing with carbon dioxide to form a carbonatewith the cation of the catalyst and removing the carbonate, and (2) fromabout 20 to 80 percent, by weight of the composition, of (a) a methylolphenyl ether corresponding to the general formula noon onion HgOH whereR represents a member of the class consisting of ethylenicallyunsaturated aliphatic radicals containing at least three carbon atomsand halogenated derivatives of the aforesaid unsaturated aliphaticradicals or (b) the methylol phenyl ether of (a) above in admixture withmethylol phenyl ethers corresponding to the general formula (CH2OH)u H.

variety of methods. Thus, they maybe prepared from compoundscorresponding to the general formula HOCHzonion a H (union where Z iseither a sodium or a barium atom. Such methylol phenyl ethers are moreparticularly disclosed in Martin Patent 2,579,330 assigned to theassignee of the present invention. Thus, these ethers may be prepared byetfecting reaction between either the sodium salt or barium salt oftrimethylol phenol with the particular organic halide desired in orderto replace the sodium or barium cation with the organic residue of theorganic halide.

In order that those skilled in the art may better understand how thepresent invention. may be practiced, the following examples are given byway of illustration and not by way of limitation. The following examplesillustrate the preparation of various ethers coming within the scope ofthe above-identified general formula. All parts are by weight.

Example I To 210 parts by weight of sodium 2,4,6-tris (hydrOx'y methyl)phenate was added a solution of parts by weight of allyl bromide in 475parts by weight of methanol. The mixture was refluxed with stirring fortwo hours. The methanol was distilled off under vacuum and amyl alcoholadded. The amyl alcohol solution was washed with a solution of saturatedsodium carbonatepotassium chloride and was dried over anhydrous sodiumsulfate; The amyl alcohol'was removed under vacuum. The product,l-allyloxy-2,4,6-tris (hydroxymethyl) benzene, was a brown syrup.

Example II 42 parts by weight of the sodium 2,4,6-tris (hydroxymethyl)phenate were mixed with 40 parts by volume of 2.5 percent solution ofsodium hydroxide. by weight of Z-methallyl chloride were added. Thereaction ingredients were shaken at 55 C. for 48 hours. The cooledreaction product was added to 200-300 parts byweight of hot water,heated for a short period and stirred. An oily layer was recovered,washed and dis solved in acetone, filtered, and the water and acetonedis'- tilled off. The product, 1-(2'-methallyloxy)#2,4,6 tris(hydroxymethyl) benzene, was a very viscous, almost solid brown syrup.

Example III Example II was repeated using 23.3 parts by weight of2,3-dichloropropene in lieu of the Z-methallyl chloride. Methanol wasnot used. The product, 1-(2'-chloroallyl-. oxy)-2,4,6-tris(hydroxymethyl) benzene was a viscous brown syprup.

Example IV 1-(3'-chloroallyloxy)-2,4,6-tris '(hydroxyniethyl) benzene, aviscous brown syrup; was prepared by repeating Example II using1,3-dichloropropene in lieu of the 2- methallylchloride and without theuse of methanol.

Example V To the solution were added 164 parts sodium hydroxide in partswater and the whole reacted for six and onehalf hours at 40 C. Threehundred and three parts by weight of allyl chloride were then added andthe mixture reacted in a pressure reactor-at 60 C. for three hours withvigorous stirring. The aqueous layer was drawn off and the organic layerdehydrated by heating under a vacuum. v I

It will, of course, be apparent to those skilled in the art that byvarying the conditions of reaction, for example, by employing adifferent temperature or a shorter or longer reaction period and also byaltering the molar ratios of the reactants, yields containing varyingpercentages of the allyl (hydroxymethyl) phenyl ethers may be obtained.Thus, by a proper choice of conditions, it is posible to preparereaction products comprising from 5 to 60 percent, by weight of allyloxytris (hydroxymethyl) benzene, and to 40 percent, by weight of each ofthe allyl uniand bis (hydroxymethyl) benzenes. The methylol phenylethers described above are used in conjunction with certain specificliquid phenolaldehyde resins in preparing the novel laminating resinsand varnishcs of my invention. Among the liquid resins coming within thescope of the instant invention are the liquid products of partialreaction of ingredients comprising a phenol, within the meaning of whichterm is included, for instance, phenol (C H OH) itself, m-cresol,3,5-xylenol, resorcinol, etc., as well as mixtures of phenols, and amolar excess of an aldehyde, e.g., formaldehyde, acetaldehyde, furfural,etc., as well as mixtures of aldehydes. The preferred reactants arephenol and formaldehyde. I

The phenolic resins are prepared in the presence of either barium orcalcium hydroxide catalysts, barium hydroxide being preferred. Uponreaching a predetermined viscosity, that of the A stage resin, thecatalyst is neutralized by introducing into the reaction product carbondioxide, preferably in excess. The carbon dioxide may be introduced inthe form of either a gas or a solid (Dry' Ice). The carbon dioxide formsan insoluble carbonate with the calcium of barium ions and may be easilyremoved in [conventional fashion, as by filtration or cent'rifuging. Theneutralized and filtered resin solution is then preferably subjected toheat and'vacuum to remove some of the water or other solvent and toremove the excess carbon dioxide. Theproduct is a resin almosttotallyfree of soluble ions and having a pH in the range of 5 to 7,preferably about 6.5. I The following examples illustrate thepreparation of phenolic resins useful in this invention. All parts areby weight. Example VI To 51 parts of 37.2% formaldehyde 0.76 part ofbarium hydroxide was added and after the barium hydroxide was insolution, 45.9 parts of phenol were aded. The mixture was then heated,allowed to boil and refluxed for about an hour and a quarter. 26 partsof carbon dioxide were then added until the pH was about'6.5. Theresulting resin was then filtered to remove the BaCO suspension. Thefiltered resin was then subjected to vacuum and heated untilapproximately 10 parts of condensate had been distilled oif. Theresulting resin had a specific gravity of 1.l6-1.2 at 25 C. and aviscosity of 200-300 cp. at 25 C. The resin solids was approximately 68to 72%.

Example VII The amount of methylol phenyl ether which may be used withthe foregoing phenolic resins may be varied within wide limits withoutdeparting from the scope of the invention. On a weight basis, the mo Ofmethylol aesaeeo l phenyl ethers employed may vary, for instance, fromabout 20 to 80 percent of the total weight of the combined methylolphenyl ethers and the aforementioned phenolic resins. Generally, Iprefer to use from 40 to 60 percent by weight, of the ethers, based onthe combined weight of the latter and the resin. If desired, and wherenecessary, the methylol phenyl ethers and the resin may be dissolved ina suitable solvent in order to blend the material together prior tofurther processing.

The following examples illustrate the improvements in heat resistanceobtained by adding the unsaturated methylol phenyl ethers to the abovedescribed phenolic resins and forming laminates with the resultingcomposition.

Example VIII Mixed ethers comprising the reaction product of Example Vwere mixed in equal parts with the phenolic resin prepared as in ExampleVI and a laminate (Lam. 1 in table below) prepared using glass cloth.Another laminate (Lam. 2 in table below) was prepared using the phenolicresin of Example VI alone. Each of the laminates 1 and 2 had a resincontent of from 37-40%, were laminated at a temperature of -165 C. and alow pressure of approximately 25-30 p.s.i. They were then post-cured for24 hours at l25-130 C. and tested for their heat resistance by placingthem in an oven at 250 C. and observing the loss in flexural strength.The results were as follows:

Lam l Lam. 2

Flex'ural strength, original (p.s.i.) 47, 400 51, 400 Flexural strengthafter 3 days at 250 0 26, 930 26. 630 Percent drop in strength 43. 2,48. 2 Flexnral strength after 7 days at 250 C 17, 860 13, 750 Percentdrop in strength 62. 3 73.1 Flexural strength after 10 days at 250 13,620 11. 870 Percent drop in strength 71. 2 76. 8

The above results illustrate the unexpected improvement in heatresistance obtained by using the compositions of this invention. Thedrop in fiexural strength was less for the laminates of this invention(Lam. 1) at the end of each of the periods above recorded. At the end of10 days, the laminate of this invention retained a higher percentage ofits original strength than the laminate prepared with the phenolic resinalone. It should be noted that the above tests were repeated over adozen times and the results were found to be consistent andreproducible.

7 Example 1X The following example compares the heat resistance oflaminates molded under higher pressures. Each of the following glasscloth laminates (Lam. 3, Lam. 4 in table below), had a resin content of38%, were laminated Lam. 3 Lam. 4

as, 750 Y 49, see

Flexnral strength, original (p.s.i.) Flexural strength after 3 days at250 C Percent drop in strength 53. 3 Floxural strength after 7 days at250 0 27, 020 13, Percent drop in strength 52. 3 73. 2

The above experiment further indicates the marked improvement in heatresistance achieved by the resinous compositions of this invention. Inaddition to retaining a higher percentage of its fiexural strength underprolonged exposure to heat, laminate 3 has a final flexural 5 morethantwice that of laminate 4, afterseven days" exposure. Example X Afurther test was conducted in order to ascertain whether phenoliclaminating resins other than those above described as useful inthe-practice of this invention would achieve improved heat resistancewhen modi- .fied with methylol phenyl ethers. A phenolic resin wasprepared by reacting an excess of formaldehyde with phenol in thepresence of ammonium'hydroxide as catalyst. The resulting resin had aspecific gravity of about LOSS-1.060, a viscosity at 25 C. of about100-250 cps. and resin solids content of 56-58%. This resin was thenmixed with the methylol phenyl ether of Example V and a laminateprepared. After less than two hours of exposure at a temperature of 250C., the laminate blistered so that strength tests could not be testindicates the importance of using phenolic resins prepared in 'themanner above set out. While the reason for 'the necessity of thespecific phenolic resins indicated is not fully known, it is believedthat resins prepared by the method of the present invention areparticularly stable because of the absence of catalyst or neutralizationions and because of the substantial absence of acidity or alkalinity.

While the foregoing examples illustrate the unexpectedly enhanced heatresistance of laminates prepared in accordance with this invention, itshould also be noted that the chemical resistance of laminates is alsoimproved if the compositions of this invention are employed. Thus,laminates made with a mixture of methylol .phenyl .ethers and thephenolic resins of this invention have been .found to have improvedresistance to caustic, to ammonia, to sulftu'ic, hydrochloric and nitricacids and to hydrogen peroxide.

While the mixed allyl ethers have been found to be very useful informing the novel compositions and laminates of my invention, otherhereinbefore-described unsaturated ethers can also be advantageouslyemployed.

The principal reason for using the described .mixture is due to theexpense involvedin separatingand producing each of the ethers in thepure state. However, as above set out, the single methylol phenyl ethersmay also be employed.

In addition to the resins previously described, illustrative examples ofother liquid, .thermosetting phenolic resins which may be employed inthe process of invention include the liquid, barium or magnesiumhydroxide catalyzed products ofpartialreaction of:

Phenol and furfural m-Cresol and formaldehyde m-Cresol and furfural3,5-xylenol and formaldehyde 3,5-xylenol and furfural Phenol,formaldehyde and furfural Phenol, resorcinol and formaldehyde Phenol,resorcinol and furfural Phenol, formaldehyde and acetone Phenol,formaldehyde and acetaldehyde Phenol, phenyl phenol and formaldehydePhenol, alpha-phenylethyl phenol and formaldehyde Phenol, m-cresol,formaldehyde and furfural 82% phenol and furfural 82% pheno formaldehydeand furfural.

As above described, the phenolic resins are prepared by reacting, in thepresence of the barium or calcium hydroxide, an excess of the aldehydewith a phenol, the molar ratio of aldehyde to phenol being ordinarilyabout 1.1 to 2.0 mols of aldehyde to 1.0 mol phenol. The resin is thenneutralized with CO and its resin solids content suitably adjusted.

While the preferred laminates are those made from glass cloth, otherconventional laminating materials may be used, including micaceous sheetmaterial, polyester made. This film, asbestos, glass thread reinforcedropepaper and ici lther well-known sheet material made from inorganiclers.

The initial thermosetting compositions. and laminates of the instantinvention have a wide field of utility. The initial compositions can beapplied as a coating to various materials where it is sought to impartits exceptionally good heat and chemical-resistant properties. They canbe used either with or without a solvent to coat various surfaces bybrushing, dipping or spraying. The cast compositions find a wide varietyof uses. For instance, they can be used as potting compositions forelectrical coils and for casting numerous other articles such as cutleryhandles, tool handles, etc. Laminates of the instant invention, as isevident from the foregoing description, have great utility in hightemperature applications, for instance, for various constructional,decorative and insulation purposes. One use of the laminates is as asubstitute for aluminum in the construction of military aircraft wherethe ability to retain mechanical strength at elevated temperaturesduring high speed flight is a basic requirement. What I claim as new anddesire to secure by Letters Patent of the United States is: t

1. A resinous composition comprising (1) a thermosetting, partiallyreacted, liquid phenolic resin prepared by reacting a phenol selectedfrom the class. consisting of phenol, alkyl and aryl substitutedmonohydroxy phenols, unsubstituted dihydroxy phenols and mixturesthereof with an excess of an aldehyde selected from the group consistingof saturated aldehydes and mixtures thereof in the presence of acatalyst selected from the group consisting of calciumand bariumhydroxide, neutralizing with carbon dioxide to form a carbonate with thecation of the catalyst and removing the carbonate, and (2) from about 20to percent by weight of the composition, of a methylol phenyl ethercorresponding to the general formula HOCH CHxO-H H H (iiHsOH where Rrepresents a member of the class consisting of ethylenically unsaturatedaliphatic radicals containing from three to' about four carbon atoms,and halogenated derivatives of the aforesaid unsaturated aliphaticradicals.

2. A resinous composition comprising (1) a thermosetting, partiallyreacted, liquid phenolic resin prepared by reacting a phenol selectedfrom the class consisting'of phenol, alkyl and aryl-substitutedmonohydroxy phenols, unsubstituted dihydroxy phenols and mixturesthereof with an excess of an aldehyde selected from the group consistingof saturated aldehydes and mixtures thereof in the presence of acatalyst selected from the group consisting of calcium and bariumhydroxide, neutralizing with carbon dioxide to form a carbonate with thecation of the catalyst and removing the carbonate, and (21' from about20 to 80 percent by weight of the composition, of a mixture ofingredients comprising (a) a methylol phenyl ether corresponding to thegeneral formula HOCHs CH;OH

CHzOH where R represents a member of the class consisting ofethylenically unsaturated aliphatic radicals containing from three toabout four carbon atoms, and halogenated derivatives of the aforesaidunsaturated aliphatic radicals,

. 7 and (b) methylol phenyl ethers corresponding to the general formulaY a where n is an integer of the group consisting of 1 and 2, and R hasthe meaning given above.

3. The resinous composition of claim 1 in which the phenolic resin isprepared by reacting phenol with formaldehyde in the presence of bariumhydroxide as the catalyst.

4. The resinous composition of claim 2 in which the phenolic resin isprepared by reacting phenol with formaldehyde in the presence of bariumhydroxide as the catalyst. v

5. The resinous composition of claim 3 in which the methylol phenylether comprises l-allyloxy-2,4,6-tris(hydroxymethyl) benzene.

6.' A laminated sheet material comprising a plurality of superimposedsheets adhesively secured together and coated with a compositioncomprising (1) a thermosetting, partially reacted, liquid phenolic resinprepared by reacting a phenol selected from the class consisting ofphenol, alkyl and aryl substituted monohydroxy phenols, unsubstituteddihydroxy phenols and mixtures thereof with an excess of an aldehydeselected from the group consisting of saturated aldehydes and mixturesthereof in the presence of a catalyst selected from the group consistingof calcium and barium hydroxide, neutralizing with carbon dioxide toform a carbonate with the cation of the catalyst and removing thecarbonate, and (2) from about 20 to 80'percent by Weight of thecomposition, of a methylol phenyl ether corresponding to the generalformula I mon where R represents a member of the class consisting ofethylenically unsaturated aliphatic radicals containing from three toabout four carbon atoms, and halogenated derivatives of the aforesaidunsaturated aliphatic radicals.

7. A laminated sheet material comprising a plurality of superimposedsheets adhesively secured together and coated with a compositioncomprising (1) a thermosetting, partially reacted, liquid phenolic resinprepared by reacting a phenol selected from the class consisting of 8phenol, alkyl and aryl substituted monohydroxy phenols, unsubstituteddihydroxy phenols and mixtures thereof with an excess of an aldehydeselected from the group consisting of saturated aldehydes and mixturesthereof in the presence of a catalyst selected from the group consistingof calcium and barium hydroxide, neutralizing with carbon dioxide toform a carbonate with the cation of the catalyst and removing thecarbonate, and (2) from about 20 to percent by weight of thecomposition, of a mixture of ingredients comprising (a) a methylolphenyl ether corresponding to thegeneral formula where R represents amember of the class consisting of ethylenically" unsaturated aliphaticradicals containing from three to about four carbon atoms, andhalogenated derivatives of the aforesaid unsaturated aliphatic radicals,and (b) methylol phenyl ethers corresponding to the general formulaHGl-n) 2 0 n where n is an integer of the group consisting of 1 and 2,and R has the meaning given above.

8. The laminated sheet material of claim 6 in which the phenolic resinis prepared by reacting phenol with formaldehyde in the presence ofbarium hydroxide as the catalyst.

9. The laminated sheet material of claim 6 in which the sheets are glasscloth.

9 References Cited in the file of this patent UNITED STATES PATENTSOTHER REFERENCES Chase: Article in Ofiicial Digest, March 1952, page172.

Chem. Eng. New, volume 30 (1952), page 4986.

DAlelio: Experimental Plastics and Synthetic Resins, page 158, JohnWiley & Sons, New York, 1946.

6. A LAMINATED SHEET MATERIAL COMPRISING A PLURALITY OF SUPERIMPOSEDSHEETS ADHESIVELY SECURED TOGETHER AND COATED WITH A COMPOSITIONCOMPRISING (1) A THERMOSETTING, PARTIALLY REACTED, LIQUID PHENOLIC RESINPREPARED BY REACTING A PHENOL SELECTED FROM THE CLASS CONSISTING OFPHENOL, ALKYL AND ARYL SUBSTITUTED MONOHYDROXY PHENOLS, UNSUBSTITUTEDDIHYDROXY PHENOLS AND MIXTURES THEREOF WITH AN EXCESS OF AN ALDEHYDESELECTED FROM THE GROUP CONSISTING OF SATURATED ALDEHYDES AND MIXTURESTHEREOF IN THE PRESENCE OF A CATALYST SELECTED FROM THE GROUP CONSISTINGOF CALCUIM AND BARUIM HYDROXIDE, NEUTRALIZING WITH CARBON DIOXIDE TOFORM A CARBONATE WITH THE CATION OF THE CATALYST AND REMOVING THECARBONATE, AND (2) FROM ABOUT 20 TO 80 PERCENT BY WEIGHT OF THECOMPOSITION, OF A METHYLOL PHENYL ETHER CORRESPONDING TO THE GENERALFORMULA
 9. THE LAMINATED SHEET MATERIAL OF CLAIM 6 IN WHICH THE SHEETSARE GLASS CLOTH.